Septic systems are extensively used to treat sewage from individual residences and businesses in areas not served by sewers. In the treatment of sewage by such septic systems, solid and liquid waste from the residence or business is collected in a septic tank in which, because of their different densities, the solid and liquid components of the sewage separate. The solid material is decomposed within the tank by the action of anaerobic bacteria, resulting in a liquid effluent. The liquid effluent is then conveyed out of the tank and distributed through an area of subterranean soil, which is frequently referred to as a drain field, and the liquid effluent then percolates through the soil and becomes purified before again joining the underground water table.
U.S. Pat. Nos. 7,040,840; 6,886,588; 6,749,743; 6,277,280; 5,647,986; 5,597,264; 5,290,434; 4,614,584 and 3,956,137; and Japanese Patent No. JP 411014513A relate to septic systems and various aspects of their operation.
In practice, sewage drain fields are generally divided into a number of portions, (frequently referred to as fingers, as in this application), and the effluent is distributed to the portions, or fingers, and over a wide area to avoid oversaturation of a portion of the drain field. In systems where the drain field is divided into a plurality of fingers, it is common to include in the system a distribution tank to receive the effluent from the septic tank and to distribute it to the plurality of fingers forming the drain field.
In the past, such effluent distributions have comprised a tank having an inlet connected with the effluent outflow of the septic tank and with a plurality of outlets distributed around the periphery of the bottom of the tank, which are connected by underground tubing or piping to the various fingers of the drain field. It is not uncommon, however, for the ground under such a distribution tank to settle, allowing the distribution tank to be tilted so that only one or a few of the fingers of the drain field receive all or a substantially greater part of the effluent outflow of the septic system. In addition, grease, mold, bacteria and other non-fluid waste can collect and grow in or on adjacent outlets of the distribution tank and restrict, and sometimes block, the flow of effluent from outlets of the distribution tank, creating a non uniform flow of effluent to the drain field. Under such conditions, the soil affected by the portion of the drain field receiving excess effluent can become saturated, requiring service of the septic system and possibly modification of the drain field. Because of the required excavation, re-installation of the distribution tank and the possible installation of new underground pipes, the servicing and modification of the sewage system can be expensive. The life of a septic system drain field can be substantially extended if the effluent from the septic system is uniformly distributed in the drain field.
U.S. Pat. No. 7,040,840 discloses means for distributing effluent more uniformly to a plurality of portions or fingers of a drain field.